Sexual differentiation is important to most aspects of an animal's life and is an interesting problem in developmental genetics. In the nematode Caenorhabditis elegans, sex determination depends on the ration of the number of X chromosomes to the ploidy of the animal, termed the X/A ratio. The signal for sex determination consists then of two parts: X-linked feminizing elements and autosomal masculinizing elements. By microinjectin DNA from the X chromosome, six feminizing elements have been defined. All of these have an identical eight base sequence. This octamer itself is als feminizing when microinjected. One current project is to test sequences related to this octamer and to define the minimal and optimal feminizing sequence. A second project is to determine how this octamer sequence is distributed in the genome. If the octamer is part of the X/A ratio, it wil be more prevalent on the X chromosome than on the autosomes. One of the major goals is to determine how this sequence functions in sex determination. One way to approach this goal is to identify proteins that bind to the feminizing sequence and define the genes that encode these proteins. These genes may include the autosomal masculinizing elements. The long-term goal is to determine the mechanism of the X/A ration in C. elegans and the relationship between sex determination and dosage compensation. Identifying a sequence involved in sex determination is a major step towards that goal.